Alien Soldier is a 1995 side-scrolling run and gun video game developed by Treasure for the Mega Drive. Retail copies were released in Japan and PAL territories while in North America it was only available exclusively via the Sega Channel cable service. The story follows a powerful being named Epsilon-Eagle, who after being nearly killed becomes determined to avenge his near death and save his planet. The character has a variety of weapons and moves that the player must master to complete the game. Many gameplay ideas are borrowed from Treasure's earlier Mega Drive release, Gunstar Heroes. However, Alien Soldier puts an emphasis on challenging boss fights with short and easy levels serving as downtime in-between.

Development lasted two years and was led by Hideyuki Suganami, who originally wanted to make the entire game himself but ultimately received support. He had ambitious plans for Alien Soldier but in order to meet his deadline, the game was released at roughly half-completion. Alien Soldier was released towards the end of the Mega Drive's lifecycle and was explicitly targeted for "hardcore" Mega Drive gamers. Critics have praised the game for its graphics, soundtrack, and overall intensity, recommending it for fans of Gunstar Heroes and the run and gun genre. Some negative critique was directed towards the hard difficulty, steep learning curve, and unorthodox gameplay. It was ported to the PlayStation 2 in Japan, and also re-released worldwide on the Wii Virtual Console and Steam.